Project description
Background. Permanent, plastic deformation in metals is the result of the collective motion of a large number of dislocations. Dislocations are curve-like defects in the atomic lattice of the metal, which move in response to applied and internal stresses. In this project we aim to connect two different descriptions of this phenomenon. At the fine scale, the dislocations are represented individually; at a coarse scale, only by continuum densities. The former is more accurate, but too detailed for most practical purposes. The latter is practical, but current models at the coarse scale are phenomenological in nature and hence the exact connection with fine-scale models is unclear.
Project objective. In this project we will establish a thermodynamically consistent coarse-graining of the fine-scale, discrete-dislocation models towards a coarse-scale, continuum plasticity formulation by employing the framework of the General Equation for the Non-Equilibrium Reversible-Irreversible Coupling (GENERIC; see H.C. Öttinger, Beyond Equilibrium Thermodynamics, Wiley, 2005). This methodology is based on non-equilibrium statistical mechanics and uses ensemble theory and projection operator methods to arrive at the coarse-scale description. It was first and mainly applied to complex fluids; here we extend its application domain to crystalline solid materials. This will allow us to obtain a full coarse-scale dynamics of dislocation-mediated plasticity which is thermodynamically consistent with the underlying, fine-scale physics.
Project plan. The main steps to be taken in the project follow the GENERIC scheme of coarse graining, namely:
- Identification of the proper variables on the coarse level which are of relevance for the targeted mechanical properties.
- Derivation and study of the thermodynamic state functions on the coarse level. To this end, classical statistical mechanics with extended ensembles will be used.
- Determination of the kinematics by appropriate choice for the Poisson operator by coarse graining or by purely coarse-scale considerations.
- Inclusion of dissipative effects, e.g., dislocation motion, dislocation reaction, and thermal conduction, by specification of a generalized friction matrix.
- Application of the coarse grained model to creep deformation and cyclic loading; comparison and validation with experimental data.
Context. The work is part of a larger project in the NWO “Complexity” program on “Correlating fluctuations across the scales” and will be done in close collaboration with Dr. Adrian Muntean and Prof. Mark Peletier of the Department of Mathematics and Computer Science. A companion PhD student at this department will be contributing to reach the same objective, but via a different route, which places more emphasis on mathematical rigour. In both parts of the project, dislocation-mediated plasticity is a model for a larger class of problems in which the emergence of coarse-scale features and slow dynamics from fine-scale behaviour cannot be understood via classical multiscale methods. By focusing on dislocations we expect to develop new methods that will be applicable to a wider range of complex systems.
Requirements
We are looking for a candidate with an MSc in Physics with a strong background and interest in statistical physics and affinity with mechanics and materials; candidates who hold a degree in Materials Science, Mechanical Engineering or related disciplines and have a documented strong background in statistical physics can also apply. The candidate is expected to be outstanding, highly motivated, and goal-oriented, with strong analytical skills. Good communication and writing skills in English are a prerequisite.
Appointment and salary
We offer a full-time appointment for four years as a university employee in an enthusiastic, multidisciplinary team. Your gross salary will start at €2,042 per month in the first year and increase to €2,612 in the fourth year. Fringe benefits offered by the university include an end-of-year allowance, support for personal development and career planning, child care and excellent sports facilities.
More information
More information about the section Mechanics of Materials can be found at www.mate.tue.nl.
For further information about the position please contact:
- Prof.dr.ir. M.G.D. Geers, +31 40 247 5076, M.G.D.Geers@tue.nl
- Dr. sc. nat. M. Hütter, +31 40 247 2486, M.Huetter@tue.nl
- Dr.ir. R.H.J. Peerlings, +31 40 247 2788, R.H.J.Peerlings@tue.nl
Application
Your well-prepared and convincing application should include:
- a brief letter explaining motivating your interest in the position
- a detailed curriculum vitae
- a complete list of courses taken and grades obtained (including transcripts of academic records)
- contact details of two references
- any other relevant information
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